EMI: Make attached objects use their parents sort order

This makes it so that things guybrush is holding correctly get rendered behind things, but it also breaks the rendering in some places

![untitled](https://f.cloud.github.com/assets/240865/1646236/28eeed3e-5915-11e3-9bc5-86f307344d43.png)

Note that the ripples are drawn on top of the boats. That could be a related bug, or it could just be broken by the new behavior...